Add release notes page for version 30.0.0

Tempest 30.0.0 has been released [1].
This commit adds a new page for 30.0.0 release notes.

[1] https://review.opendev.org/c/openstack/releases/+/832742

Change-Id: I52e84d8626a39e8ad8690185dc12cfd8d8654c9b
diff --git a/releasenotes/source/index.rst b/releasenotes/source/index.rst
index 3bff257..122f7c7 100644
--- a/releasenotes/source/index.rst
+++ b/releasenotes/source/index.rst
@@ -6,6 +6,7 @@
    :maxdepth: 1
 
    unreleased
+   v30.0.0
    v29.2.0
    v29.1.0
    v29.0.0